A fluid circulation system is generally configured to circulate a fluid. For example, a fluid circulation system can be coupled to a HVAC system to help circulate a process fluid (such as water) between a terminal device (such as a room unit) and an outdoor unit, which may include an evaporator coil, of the HVAC system. The fluid circulation system may generally include one or more pumps to provide and/or regulate a fluid flow.
To control the fluid circulation, typically, a user can set up a fluid pressure differential setpoint between two pressure measuring points in the fluid circulation system so as to control a capacity (or flow rate) of the fluid circulation system. Generally, the higher the fluid pressure differential setpoint is, the higher the fluid flow rate provided by the fluid circulation system.
In some situations, the fluid circulation system may be configured to provide and/or maintain a certain fluid flow rate. For example, in the fluid circulation system that is configured to circulate the process fluid (such as water) through an outdoor unit of a HVAC system, it may be desirable to maintain a certain fluid flow rate to an evaporator coil of the outdoor unit. The fluid flow rate may depend on, for example, a cooling capacity of the HVAC system. Generally, the larger the cooling capacity is, the higher the desired fluid flow rate. A user may set a desired fluid pressure differential setpoint in the fluid circulation system so that the fluid circulation system may provide and/or maintain a relatively constant fluid flow rate that is desired for the cooling capacity provided by the HVAC system.